I have a friend who wants to bring his two year old on a 6 day backpack next summer. Last summer we saw some people in King's Canyon with a little kid riding a llama. Anyone with experience with llamas? Can you rent one?

Many locations rent llamas, but usually just for gear. Google around the area, but then ask specifically about hauling a child. Llamas are intelligent, particular, and sometimes belligerent. If not "child ready", I would not risk it.

Transportation can also be an issue. It is easiest if they can meet you at the trailhead. Otherwise you will need at least a small truck.

If llamas become too much of a problem, the other alternative would be the human porter. My friends have a kid that was brought along on all backpack trips from age 3 months on. The backpack baby carrier was the key. Once the kid gets too heavy to carry, then the kid is probably big enough to walk some miles on their own.
Since the dad got to carry the kid for those couple of years, they always recruited a human porter (me) to help carry the remaining gear load.
Once the kid got to be four or so, there was no further use of the baby carrier.
–B.G.–

I've also seen donkeys being led along the trail in Kings Canyon (Goddard Canyon). Obviously they are smaller animals, so they can't carry extremely heavy loads, but if they carry the gear, then dad can carry the kid. There is some place that rents donkeys, but (as I recall) you have to deposit some horrendous pile of cash and submit to some training. Donkeys are such docile animals that few hikers would object. OTOH, check with NPS first.
–B.G.–

I did find a guy named Greg Harford in Sonora, CA that rents llamas. The cost is $55/day per llama and they can carry up to 75lbs. There are others listed in a website as well: http://www.bcllama.com/Rlsorc.html

Bob, do you rent out cheaper than this???

Greg does not want kids to ride them though for liability reasons but the parent can carry the kid while the llama carries the equipment.

Sonora is just west of Emigrant Wilderness and I think that would be about the only place that this would be feasible in California. Emigrant is a beautiful place but it does not seem very challenging and there are no trail quotas so it's probably crowded in the summer. They are fine with llamas though.

"Obviously they are smaller animals, so they can't carry extremely heavy loads,"

Donkeys can carry way more than Llamas. A lot of Llamas cant pack as much as goats that are half their size. Just me, but if I did not own, and know that Llama very well, I would not put my kid on. I'd say Llama for gear, Donkey for riding.